1. Field of the Invention
The present invention relates to an a method for blending and windrowing hot plant mix asphalt used in paving and resurfacing roadways.
2. Discussion of the Related Art
Hot plant mix asphalt is a material commonly used throughout the country to pave and resurface roadways. Advancements in asphalt technology, both in the manufacturing of equipment and in the construction process, have enabled road builders to improve the construction and performance of modern highways, particularly in respect to smoothness and uniformity of the road surface. Smoothness of the surface directly affects both noise levels from vehicles traveling on the road and longevity of the surface. In fact, most roadways are now constructed in accordance with strict performance parameters concerning, among other items, smoothness, uniformity, and longevity. Moreover, many specifying agencies have adopted bonus plans for contractors who meet or exceed such performance parameters to earn extra pay, or in contrast, penalties for those who do not.
The processes for producing asphalt and paving roadways include mining and crushing aggregate material, grading and blending the material, transporting and charging feeders of an asphalt plant, reblending and mixing the material with hot asphalt liquid, dumping the hot asphalt into storage systems and dump trucks, hauling the material to the construction site, further dumping and transferring the material into a paver, and finally properly placing the material onto the road surface. Care must be taken at every step of the process to ensure that the material is thoroughly mixed in order to lay down a sufficiently smooth surface. From the standpoint of the road building contractor, special care must be given to the last two steps--transferring material to the construction site and the final paving process--otherwise quality is lost. Problems encountered by road building contractors which adversely affect smoothness include segregation of material, truck bumps, logistical difficulties in transporting material, and cold joints.
Hot plant mix asphalt is composed of liquid asphaltic cement mixed with different sizes of aggregate. In order for asphalt pavement to be of maximum quality, smooth and long-lasting, it must be uniformly blended, without any segregation of material. As with any type of material, hot plant mix asphalt tends to segregate with handling. Even though the material may have been thoroughly mixed and blended at the plant, the asphalt will nonetheless tend to segregate by the time it has been transported to and laid down on the road surface.
Conventional paving operations often require that a dump truck back up to a paver in order to deposit the material into the paver. Some contractors use the paver to propel both the paver and dump truck during the paving process. Occasionally the dump truck may bump into the paver, causing a momentary disruption in the paving process. The disruption results in a small bump in the road referred to in the industry as "truck bumps."
Because conventional paving operations require a dump truck to deposit asphalt directly to the paver, delivery of multiple loads of asphalt must be precisely timed so that a new, fully loaded truck arrives just as the previous truck has been emptied in order to maintain the pace of the paving operation. Disruptions in the delivery of asphalt can cause cold joints and other irregularities in the pavement.
Conventional techniques to address such problems have typically involved development of various sophisticated pieces of equipment which are extremely expensive and often add a host of other operating problems to the process. Some of those methods incorporate the use of equipment which have a large capacity for holding asphalt material. Such devices are useful in reducing the number of times that material must be transferred from a dump truck to paver, thereby reducing the number of "truck bumps" and cold joints, but not eliminating the problem altogether. Numerous other ideas have been tried with less-than-satisfying results.